In a typical coffee maker, coffee grounds are placed in a conical filter which is held in a cup located directly below a heated water dispenser. Tap water is poured over a heating coil located in a heating chamber of the hot water dispenser which elevates the temperature of the water to approximately 180.degree. F., after which the heated water exits the heating chamber of the coffee maker and mixes with coffee grounds located below the heating chamber. The heated water mixes with the coffee grounds and passes through the conical filter to a coffee pot positioned below the coffee grounds holding cup. The hot coffee is collected within the coffee pot located on a heating plate. The heating plate includes an electrical coil generating heat to keep the coffee in the coffee pot hot.
The object of the heating plate is to keep the coffee at a temperature satisfactory for most coffee drinkers. The heating plate underneath the coffee pot generates a temperature of approximately 250.degree. to 350.degree. F. The heat given off from the heating plate is transferred through the bottom of the coffee pot to the coffee.
The constant exposure of the coffee, in the coffee pot, to the heat generated by the heating plate produces many disadvantageous results. The heating plate generates a temperature in excess of the boiling point of coffee, and will boil away the coffee in the coffee pot over a period of time. Further, exposure to the 250.degree. to 350.degree. F. heat generated by the heating plate causes coffee crystals at the bottom of the coffee pot to burn over a relatively short period of time. The burned coffee crystals circulate throughout the pot of coffee and affect the taste of the coffee being heated in the coffee pot. Further, the deteriorated crystals can collect at the bottom of the coffee pot to form an unsightly residue. A coffee pot will also crack due to continuous exposure to heating and cooling of the coffee pot if the pot is left on the heating plate after the contents of the pot have been boiled away by the heat generated by the heating plate.
This problem is also pervasive in the food industry where solid and liquid food are required to be maintained within a certain temperature range below 212.degree. F., either for storage or for serving. Exposure to temperatures above 212.degree. F. will dry out or cause the boiling away of the contents of a pot, pan or container holding the food and cause spoilage of the food.
To overcome extended exposure to elevated temperature conditions for liquids, attempts have been made to lower the temperature of the heat source. Lower temperature heat sources have been found to maintain brewed coffee or other food items at a temperature which is unsatisfactory.
It is an object of the present invention to overcome the disadvantages of present food warming systems for food holding containers.
It is an object of the present invention to provide a method for transferring heat through a double walled container.
It is another object of the present invention to maintain the temperature of the contents of a liquid container at approximately 180.degree. F.
It is yet another object of the present invention to transfer a quantity of heat generated by an electric heating plate at a temperature of approximately 250.degree. to 350.degree. F. to a container to maintain the temperature of the contents of the container at approximately 180.degree. F.
It is still another object of the present invention to provide a double walled enclosure surrounding a bottom portion of a container.
It is still yet another object of the present invention to provide a heat-transfer liquid which does not boil or vaporize substantially at temperatures up to 600.degree. F. within a sealed cavity of a double walled enclosure surrounding the bottom portion of a container
It is still yet another further object of the present invention to provide a heat-transfer liquid which transfers heat from a heating source, at a temperature of approximately 250.degree. to 350.degree. F., to a liquid in a container to maintain the liquid at a temperature of approximately 180.degree. F.